It is known that aromatic diamines can be used to cure epoxy resins but that the practical utility of any aromatic diamine in this regard is dependent on factors such as its relative toxicity, its pot life in admixture with the epoxy resin, its reactivity, and the physical properties which it imparts to the cured resin. It is also known that the reactivity of an aromatic diamine curing agent can be increased by the use of an accelerator but that the presence of an accelerator in an epoxy resin/aromatic diamine composition shortens its pot life, sometimes to the point where the composition is no longer suitable for use in various operations, such as filament winding.
Among the accelerators that have been used to speed the cure of epoxy resin with aromatic diamines are complexes of boron trifluoride with monoamines such as aniline and ethylamine. As mentioned in U.S. Pat. No. 4,447,586 (Shimp), these complexes have the disadvantage of tending to crystallize or precipitate out from solutions in hindered aromatic diamines on standing.